The present invention relates to a semiconductor chip carrier for use in supporting a semiconductor chip, and to a semiconductor device and an apparatus which includes the semiconductor chip carrier and the semiconductor device, respectively.
A semiconductor chip carrier has been used in the field of semiconductor assembly technique. In such a field, a chip carrier of plastic. LCC (Leadless Chip Carrier) type has recently attracted considerable attention as a chip carrier which is applicable to a high density assembly in a circuit board, because it makes it possible to become as thin as substantially 1 mm.
A conventional LCC type chip carrier, as will later be described in detail, comprises an insulating substrate which has a rectangular shape having four corners and which has a central surface and a peripheral surface surrounding the central surface, and a plurality of electrode leads deposited on the peripheral surface. On such a chip carrier, a semiconductor chip is mounted on the central surface of the insulating substrate to form a semiconductor device. After completion of the semiconductor device, the insulating substrate is further mounted on a circuit board which has a plurality of board electrodes on a board surface. The board electrodes are electrically connected to the electrode leads on the chip carrier by the use of solder. Thus, the chip carrier is mounted on the circuit board.
In the meantime, necessity of the aforesaid high density assembly requires to make each electrode lead fine. Consequently, each electrode lead should be connected to each board electrode through a very small contact area. As a result, strength of connection between the solder and each electrode lead becomes weak with a decrease of the area between the solder end each electrode lead. For example, provided that the strength of connection by the solder is 500 g/mm.sup.2, the strength of 60 g per one electrode lead is acquired when the area of contact of the solder per one electrode lead is as small as 0.12 mm.sup.2 (0.3.times.0.4 mm.sup.2). If the number of electrode leads is between 50 and 80, the strength of connecting the package to the circuit board, as a whole, merely falls within a range between 3 kg and 5 kg. Thus, the strength of the whole connection is not so small.
However, a stress sometimes acts on the circuit board during or after an assembly process. The circuit board is sometimes twisted or warped as a result of the stress. Since the stress is concentrated on each electrode lead positioned at each of the four corners of the rectangular insulating substrate of the chip carrier, the electrode leads positioned thereat often come off the board electrodes by such a twist or warp of the circuit board. Thus, it often happens that the electrode leads are peeled off from the board electrodes at the four corners of the insulating substrate. Specifically, when the chip carrier is mounted on the circuit board which is known as a thin-type circuit board for a high density assembly and which has a thickness thinner than 0.6 mm, such a circuit board is apt to be easily twisted or warped during or after the assembly process. Therefore, the problem that the electrode leads come off the board electrodes is very serious in such a thin-type circuit board.